A prime mover, such as an internal combustion engine or the like, can be connected to a low speed, high torque hydrostatic transmission. A hydrostatic transmission is particularly suitable to provide traction drive for a vehicle, such as turf machines, lawn tractors, ride-on lawn mowers, and like devices. A simple usage of hydrostatic transmissions is on zero-turn radius vehicles, including zero-turn radius mowers and tractors.
Generally, a hydrostatic transmission includes a hydraulic pump and a hydraulic motor. The hydraulic pump usually is a piston-type pump including a plurality of reciprocating pistons which are in fluid communication through hydraulic porting with the hydraulic motor. Rotation of the hydraulic pump against a moveable swash plate creates an axial motion of the pump pistons that forces hydraulic fluid through the hydraulic porting to the hydraulic motor to drive the motor, which allows the transmission output speed to be varied and controlled. The rotation of the hydraulic motor may be used to drive an output shaft, which in turn ultimately drives a wheel axle of a vehicle of the types described above.
The hydrostatic transmission is one example of a machine component that generates heat due to rotating components and work done by the transmission. Typically, a standard fan is provided to cool an exterior housing of the hydrostatic transmission. In some cases, the standard fan is mounted to an input shaft of the hydraulic pump, which is driven by a pulley connected to the input shaft. However, in some common hydrostatic transmissions, the pulley is mounted to the shaft between the fan and the transmission housing. The pulley then acts as an obstacle that restricts airflow to the housing and impairs the cooling effect of the fan.
A general configuration of a hydrostatic transmission is shown and described in Parker-Hannifin Corporation, Cleveland, Ohio, USA, Service Manual HY13-1524-001/US, the entire contents of which is hereby incorporated herein by reference. The referenced Service Manual shows, inter alia, a basic hydrostatic transmission with a top-mounted pulley and a standard fan in exploded view at pages 10 and 11. Another general configuration of a hydrostatic transmission is shown and described in Parker-Hannifin Corporation Catalog No. HY13-1595-002/US, the entire contents of which is hereby incorporated herein by reference. The referenced Catalog shows, inter alia, a basic hydrostatic transmission with a top-mounted pulley and a standard fan at page 13, for example.